Why Is My Candle Tunneling? (And How to Fix It Properly)

Candle tunneling is one of the most common performance issues in candle making.

It occurs when wax burns straight down the center, leaving unused wax along the sides of the vessel.

While often seen as a simple defect, tunneling is usually the result of predictable variables.

What Causes Candle Tunneling

Tunneling is primarily caused by insufficient heat reaching the outer edges of the candle.

This typically comes down to:

• Wick size being too small
• Vessel diameter being too wide
• Wax formulation affecting burn behavior
• Improper first burn conditions

Each of these influences how heat is distributed during the burn.

The Role of Wick Size

Wick size is the most common cause.

If the wick is too small:

• The flame does not generate enough heat
• The melt pool remains shallow
• Wax near the vessel wall stays solid

Over time, this creates a tunnel.

Why the First Burn Matters

The initial burn cycle plays a significant role.

If a candle is extinguished before a full melt pool forms:

• A memory ring develops
• Future burns follow that pattern

This reinforces tunneling even if the wick is otherwise adequate.

Vessel Size and Shape

Wider vessels require more heat to achieve a full melt pool.

If the wick is not sized for the diameter:

• Heat cannot reach the outer edges
• The melt pool remains incomplete

In these cases, multi-wick configurations may be necessary.

Can Tunneling Be Fixed?

In some cases, yes.

Short-term fixes include:

• Allowing longer burn sessions
• Carefully correcting the melt pool with controlled heat

However, these do not solve the underlying issue.

The Proper Solution

The only reliable solution is to correct the cause.

This may include:

• Increasing wick size
• Adjusting the number of wicks
• Testing alternative wick series
• Evaluating wax and fragrance load interactions

Final Thought

Tunneling is not random.

It is the result of heat imbalance.

Correct the heat distribution, and the problem resolves.